The present invention relates to a driver circuit for an alarm tone transducer, in particular a driver stage, which can be used in vehicles containing an alarm tone system having an auxiliary battery.
Alarm tone systems in vehicles contain high-energy tone generators such as piezoelectric tweeters, horns, or loudspeakers, for emitting an audible alarm in response to different alarm or signaling (indicating) situations. These tone generators, which may be designated as alarm sirens or alarm tone transducers, are driven by a driver circuit which generates a drive signal for the siren. The driver circuits are supplied with current (power) by the vehicle battery, and the driver circuits additionally contain an auxiliary battery as emergency power supply in case the vehicle power supply to the warning system is interrupted.
A driver stage may use a tone transducer stage which includes a transformer, and which generates the signal for the alarm siren, and that is driven by a closed-loop control electronics. The voltage of the auxiliary battery, however, may dip to such an extent that it can no longer sufficiently supply the control electronics with power when the alarm siren works at maximum power. Therefore, it is desired to make a driver stage available which provides a sufficient emergency power supply without significantly increasing the cost of the circuit or which at least offers a usable alternative.
In connection with the exemplary embodiments of the present invention, a driver circuit is given for an alarm siren, the driver circuit containing the following units:
a generator for generating a first signal,
a converter for converting the first signal into a second signal for the siren,
a battery for supplying the circuit with power, and
a voltage amplifier for raising the supply voltage for the generator.
An exemplary embodiment of, the present invention concerns a driver circuit having a signal generator for generating the signal for the siren, and having a battery as power supply, the signal generator containing an inductance and a switch, in which a capacitor is connected to the inductance and to the switch, thereby resulting in a circuit for raising the voltage of the power supply.